The rotational motion of a crankshaft in an engine, along with additional connected mechanical parts such as crankpins, connecting rods and the like may produce unbalanced inertial moments and/or forces. These moments and/or forces may lead to undesirable noise vibration and harness for a vehicle operator.
One approach to balancing the inertial moments and/or forces includes providing a balance shaft rotating along an axis parallel to the crankshaft, and in a direction opposite of the crankshaft. However, the inventors herein recognize various issues related to such an approach. Balance shafts may occupy significant space in an engine block, such as when placed in a valley of a “V” engine, in a cylinder head or in a sump of the engine block. Further, if a balance shaft is disposed in a camshaft, such as in a concentric manner, rotating the balance shaft in the desired direction and at the desired speed may raise issues related to the drive system extending the overall length of the engine, exacerbating packaging space and weight problems.
Accordingly, systems, devices and methods are provided herein. In a first example, an engine includes, a camshaft, a balance shaft disposed within an interior of the camshaft, and a first gear, intermediate the balance shaft and the camshaft, the gear driving the balance shaft to rotate about a first axis substantially parallel to a crankshaft of the engine, the balance shaft further rotating in a direction opposite of the crankshaft.
In this way, it is possible to drive the balance shaft via one or more gears to provide desired rotational speed (e.g., to match the timing of the crankshaft) and reduce packaging space. Further, the first example may include additional gears configured as a planetary gear set.
In a second example, a balance mass and drive for an engine includes, a planetary gear set including a sun gear, a ring gear and a plurality of pinions mounted on a carrier, the ring gear having an interior that meshes with a first pinion of the plurality of pinions, an input coupled to an input gear of the planetary gear set, the input gear being one of the ring gear, the carrier or the sun gear, a balance mass coupled to an output gear of the planetary gear set, the output gear including one of the ring gear, the carrier, or the sun gear, the output gear different form the input gear and configured to drive the balance mass to rotate about a first axis substantially parallel to the crankshaft in a direction opposite of the crankshaft.
By utilizing a planetary gear set, it is possible to provide a compact drive that minimizes weight and packaging space of the balance mass and drive while enabling the balance mass (such as a balance shaft) to be driven at a desired speed and in a desired direction. The balance mass may include balance shafts disposed in a camshaft as well as additional masses such as weighted gears or pendulums included in the output gear, providing flexible placement of the balance mass and drive and easy adaption of such a balance mass and drive across a range of engine configurations (including “V” configurations, “I” configurations, 3, 4, 5, 6, 8, 10 and 12 cylinder engines, etc.).
It will be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description, which follows. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined by the claims that follow the detailed description. Further, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.